Photocatalytic Degradation of Contaminants with Titanium Dioxide: A 40-Year Retrospective on the Paper by John Carey and Colleagues Published in BECT

Bull Environ Contam Toxicol
Photocatalytic Degradation of Contaminants with Titanium Dioxide: A 40-Year Retrospective on the Paper by John Carey and Colleagues Published in BECT
Viviane Yargeau 0 1
Chris D. Metcalfe 0 1
0 The School of the Environment, Trent University , Peterborough, ON , Canada
1 Department of Chemical Engineering, McGill University , Montreal, QC , Canada
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John Carey is probably best known for his role over many
years to manage the science agenda within Environment
Canada. For several years, he was the Director of the
Canada Centre for Inland Waters (CCIW) in Burlington,
Ontario, Canada, and he later worked with the federal
Ministry of Environment in Ottawa to shape the policies and
research priorities of Environment Canada. However, John
Carey started his career with Environment Canada as a
researcher, and during this period, he turned his attention
to the issue of how to get rid of the large amounts of PCBs
that had been produced for decades as an additive in
transformers, hydraulic fluids and a range of other industrial
and consumer products; an issue which we still have not
addressed adequately to this day. In the paper published in
BECT in 1976 by John Carey and his colleagues at CCIW,
John Lawrence and Helle Tosine, they proposed using
titanium dioxide (TiO2) as a photocatalyst with UV irradiation
to accelerate the dechlorination of PCBs. Since its
publication, this article has gone on to be the most highly cited
research paper published in BECT, with 721 citations as of
December, 2016 (Harzing 2007).
It is astonishing that citations of this article are
accruing at an exponential rate, even 40 years after the paper
was originally published in BECT (Drouillard and
Bennett 2015). So why has this article remained relevant in the
field of photocatalysis for four decades? As the authors of
the article described in their review of progress in field of
photocatalysis at that time, there had been a small number
of articles published previously that described the potential
for using metal oxides to promote the production of
hydrogen peroxide under conditions of UV irradiation. However,
John Carey and his co-authors were the first to use TiO2
as a photocatalyst for degradation of an environmental
contaminant; in this case, PCBs. The enduring value of this
article is that they recognized that TiO2 was an appropriate
photocatalyst and they applied this technology to degrade a
chemical that was, and still is, an important environmental
contaminant.
In the last 40 years, this area of research has branched
in several directions. Since the publication of the Carey
et al. (1976) paper, their work has been cited extensively
as a seminal work guiding studies that can be classified as
research on (i) the properties and mechanisms of
photocatalysis, (ii) other photocatalytic materials besides TiO2, (iii)
photocatalysis in combination with other oxidative
treatment technologies, (iv) photocatalytic reactor design, (v)
TiO2-based composite materials, (vi) TiO2 photocatalysis
for specific treatment applications, (vii) different forms and
scales of TiO2 for photocatalysis. In addition, the Carey
et al. (1976) paper has been widely cited in reviews on
photocatalysis. Figure 1 shows an analysis of the proportion
of citations within each of these categories for 315 articles
extracted from SCOPUS that cited the Carey et al. (1976)
paper between 1980 and the present. These trend data show
that citations over the first decade focused primarily on
follow-up studies on specific applications of TiO2-based
photocatalysis, as well as the methods by which the
catalytic process can be enhanced. For instance, the paper by
Pruden and Ollis (1983) describes photocatalysis with
TiO2 to degrade trichloroethylene in water. However, more
recent work has shifted to developing composite materials
based on TiO2, including nanoparticles, as well as other
Fig. 1 Trends in the types of papers that cited the Carey et al. (1976) paper, divided according to the research category and the decade of
publication
photocatalytic materials and approaches, so citations in
papers that describe these types of studies have increased
over the past 1–2 decades (Fig. 1). An example is the paper
by Li et al. (2016) which focuses on the photocatalytic
capability of nanotubes that incorporate TiO2 in the
nanomaterial structure.
It is interesting that the original article was very
nonspecific about describing the form, or even the source of
the TiO2 that was used in the photocatalysis experiments.
The authors just described the reaction conditions as “equal
volumes of solution and titanium dioxide suspension (0.5%
in water) were thoroughly mixed and irradiated in a closed
glass container, usually for 30 mins”. Despite the lack of
detail, the article has endured as a touchstone for describing
fundamental research in the field of photocatalysis. BECT
strives to provide a forum where researchers can share their
ground breaking research with the scientific community.
Carey JH , Lawrence J , Tosine HM ( 1976 ) Photodechlorination of PCB's in the presence of titanium dioxide in aqueous suspensions . Bull Environ Contam Toxicol 16 : 697 - 701
Drouillard KG , Bennett ER ( 2015 ) The changing face of BECT: a citation analysis covering 1966-2009 . Bull Environ Contam Toxicol 94 : 1 - 5
Harzing AW ( 2007 ) Publish or Perish . http://www.harzing.com/pop. htm
Li T , Wang L , Chen G , Huang S ( 2016 ) Preparation and photocatalytic activity of WO3-TiO2 modified TiO2 nanotubes . Chin J Environ Eng 10 : 4309 - 4313
Pruden AL , Ollis DF ( 1983 ) Photoassisted heterogeneous catalysis: The degradation of trichloroethylene in water . J Catal 82 : 404 - 417

Viviane Yargeau, Chris D. Metcalfe.
Photocatalytic Degradation of Contaminants with Titanium Dioxide: A 40-Year Retrospective on the Paper by John Carey and Colleagues Published in BECT,
Bulletin of Environmental Contamination and Toxicology,
2017, 147-148, DOI: 10.1007/s00128-016-2021-2